Tired of fussing with layers to stay comfortable? The age-old drill can be especially bothersome in winter, as you battle the chills on descents and the sweats on climbs. Enter the ultraversatile, ultrawarm MicroTherm. It’s an 800-fill down parka that kept us toasty to about 15°F when we were on the move with only a light baselayer underneath (and in colder temps when we supplemented with midlayers or were laboring under heavy packs). But it also does what no other fully insulated jacket has been able to do successfully before: vent like mad when we’re working hard. That means that we didn’t have to futz with adding and subtracting layers in quickly changing conditions—like when the sun popped out for 10 minutes on otherwise blustery days in New Hampshire’s White Mountains. The secret is the thoughtfully designed pocket vents located on either side of the sternum (high enough to clear a pack hipbelt).

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“When unzipped, the 10.5-inch-long pockets fall magically open and cool air rushes through the mesh lining of one, across the core, and out the other,” says one tester who packed it as her nighttime insulator on a 450-mile bikepacking trip from Colorado to the Grand Canyon. And the versatility story gets better: The MicroTherm has a 12-denier nylon shell with a waterproof/breathable membrane and a tough DWR coating, so the jacket didn’t wet out or leak in spitting sleet or sodden snow. The zippers are all waterproof but didn’t require fiddling like so many do. The cut is spot on: roomy enough for layering, but tapered (not baggy), with articulated elbows to allow for reaching pole plants, and a long hem that protects the waistline. The hood fits over a helmet, yet can be cinched snugly over a bare head. Bonus points: It’s available in tall sizes. $299 ($319 for tall); 1 lb. 3 oz. (m’s M); m’s S-XXL, m’s tall M-XXL, w’s XS-XL; firstascent.com